A photolithography or lithography apparatus is a machine that applies a desired pattern onto a semiconductor substrate, usually onto a target portion of the substrate. A lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning member, such as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. The circuit pattern can be transferred onto a target portion (e.g. comprising one or more dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically achieved via imaging onto a layer of radiation-sensitive material (i.e. photoresist) provided on the substrate.
In general, a single substrate contains a network of adjacent target portions that are patterned successively. Known lithography apparatuses include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given scanning direction while synchronously scanning the substrate parallel or anti-parallel in this direction.
Although existing lithography apparatuses and methods have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.